This is more related to cleaning tools rather than chemicals but Walmart has an excellent brush set from Black Magic that is very inexpensive. I think it runs about $6 and its quite nice.

A picture of it is below. The piece at the top cleans the vents. The one in the middle is a soft horse hair type brush with a rubber thing at the end of it which is excellent for getting the wax/polish in the cracks. The last brush is a bit stronger.

I have spent $$$ on many good products from PS to klass and Maquire, all good and a few bad. I just use the BMW products and leaves a new car smell, does a good job and cost just the same more or less and works just as good. It's all in the time and care you put into it with good products of course.